Life cycle studies of Trichilogaster acaciaelongifoliae in Portugal
Acacia longifolia (Fabaceae) is native to South-Eastern Australia and has been introduced into areas with Mediterranean types climates across the world. In Portugal, it is an invasive plant species in coastal areas. Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) is a bud-galling wasp native to Australia and utilised as a biological control agent in South Africa. It can reduce seed production of A. longifolia by 90 %. In 2015, T. acaciaelongifoliae was released in Portugal using developed galls imported from South Africa. In Portugal, T. acaciaelongifoliae is now established along the coast where it reduces seed production and vegetative growth of the host plant. The life cycle of T. acaciaelongifoliae was studied for 1-year in two locations in Portugal (Pataias and São Jacinto) to evaluate how the gall wasp has adapted to the north hemisphere conditions. When T. acaciaelongifoliae was first released into Portugal, it had to align the time of adult emergence from the gall with the bud development peak period of A. longifolia which occurs in spring and early summer. Initially, T. acaciaelongifoliae had lower establishment success though this was overcome by using insects from the founding Portuguese population. The results suggest that T. acaciaelongifoliae in the northern hemisphere has a univoltine life cycle. The generations of T. acaciaelongifoliae are not completely synchronized both between and within the two locations studied. The life cycle seems to be more advanced in the site located further south, Pataias, where there are a greater number of emergence holes one month earlier compared to more northern populations. The results can be used to implement the release of the biological control agent into new locations.
Sources
Nunes AS, López-Núñez FA, Duarte LN, Marchante E, Marchante H (2024) Phenological alignment of a galling insect used as biocontrol agent for an invasive tree following hemisphere translocation. Biological Control 197,105598.